JP2002203724A - Laminated multiple transformer and differential transmission cable using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive laminated multiple transformer that can be reduced in size and height. SOLUTION: This laminated multiple transformer is provided with a plurality of transformers each of which is formed of a pair of coils which are constituted by electrically connecting conductor lines to each other via through holes made in each sheet composed of an insulator, in a laminate which is formed by laminating a plurality of sheets composed of the insulator and carrying the conductor lines on their surfaces upon each other and integrally sintering the laminate. The transformers are piled up in the direction of lamination and, at the same time, shield electrodes or short ring electrodes are arranged among the transformers. Moreover, external terminals which are connected to the paired coils are provided on the external surface of the laminate and the external terminals are arranged adjacently to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer laminated transformer and a differential transmission cable using the same.

[0002]

2. Description of the Related Art FIG. 10 shows a conventional laminated transformer.
This laminated transformer is obtained by stacking insulators and conductor lines alternately and sintering them integrally. A pair of coils 50 and 51 each electrically connecting the conductor lines constitutes a common mode choke coil. I have. Further, as shown in FIG. 11, a stacked multiple transformer having a plurality of pairs of coils has also been proposed. This laminated multiple transformer has two pairs of coils, each of which is formed by electrically stacking insulators and coil conductors and alternately sintering them integrally, and each of which has a common mode choke. Is composed. Conventionally, the common mode choke coil is often used to remove common mode noise that intrudes into an electronic device or the like and conversely flows out of the electronic device or the like.
Recently, in the study of the present inventors, a differential transmission system such as a USB (Universal Serial) has been proposed.
It has been clarified that arranging a common mode choke coil on a transmission line is effective in reducing skew noise generated at the time of signal transmission conforming to a transmission standard such as Bus) or IEEE1394.

The differential transmission system is a transmission system in which digital signals in mutually opposite directions are added to a pair of lines under no bias or under a bias. When viewed from a distance, such a pair of lines has a high frequency component. This is a digital transmission system that takes noise measures into consideration, such that radiation noise is not generated in principle because the noise is canceled out. Such a differential transmission system does not generate radiated noise in principle as described above, but radiated noise may be generated in an actual transmission cable. One of the causes of the noise is due to the imbalance of the differential transmission signal. Among the high-frequency components in the pair of digital signals described above, the difference (skew) that cannot be completely canceled out becomes a noise current. Eventually, it becomes radiation noise. The other one is that conduction noise generated by a personal computer, a peripheral device, or the like is transmitted to a transmission cable, which becomes radiation noise.

Of these radiated noises, harmful ones naturally require countermeasures. For example, JP-A-10-2
In the cable having two or more pairs of differential transmission lines disclosed in JP 08818, ferrite beads are inserted into each pair of differential transmission lines. In this differential transmission cable, when an in-phase signal is transmitted to a pair of transmission lines, a magnetic flux generated by the signal does not adversely affect other pairs of transmission lines (mutual interference).

[0005]

However, the problem of the above-mentioned method is a method of suppressing only harmful mutual interference, and it is necessary to consider skew noise caused by imbalance of differential transmission signals. As a result, radiation noise countermeasures are insufficient. Therefore, the present inventors have conceived of inserting a common mode choke coil into the differential transmission line as described above. According to this method, it is possible to reduce the skew noise while maintaining the quality of the digital signal without distorting the digital waveform.
To apply this method to a plurality of pairs of differential transmission lines, simply insert a common mode choke coil for each differential transmission line. However, this method is not preferable because the number of parts and the number of assembly steps increase. Not something. Therefore, the idea of using a multi-layer laminated transformer having a plurality of common mode choke coils in a plurality of pairs of differential transmission lines was conceived.
However, in the stacked multiple transformer shown in FIG. 11, magnetic coupling occurs between the transformers. If such a stacked multiple transformer is used for a differential transmission cable, the magnetic coupling is large and a large mutual interference occurs between the circuits to which the coil units of each group belong, and the individual circuits become independent. As a result, the quality of the electric signal to be transmitted is reduced, and as a result, the skew noise caused by the imbalance of the differential transmission signal is transmitted to another differential transmission line.

As a method of reducing the magnetic coupling between the laminated type multiple transformers, a method of providing a slit between the transformers to provide an air gap as shown in FIG. A method of inserting a material having low magnetic permeability (Japanese Patent Application Laid-Open No. H10-270256) has been proposed. However, the size of the laminated multiple transformer is remarkably reduced, and a sufficient gap between the coils for slitting is obtained. However, this method is not a practical method in view of the fact that the method is substantially difficult, and the number of steps and the yield when slits are taken into consideration. In addition, it is clear that the implementation of the laminated multiple transformer formed by laminating and integrating materials having different magnetic permeability is extremely difficult to implement in view of the consistency of the contraction rates of the materials. there were. Therefore, the present invention minimizes magnetic coupling between the transformers, suppresses harmful mutual interference between the transformers, and enables miniaturization, reduction in height, and inexpensive stacking. To provide a multiple type transformer. In addition, by using a common mode choke coil array for the configuration of the stacked multiple transformer, it is possible to reduce skew noise without deteriorating signal quality in a differential transmission cable that handles a plurality of differential transmission signals. It is to provide a differential transmission cable with a possible differential transmission line.

[0007]

According to a first aspect of the present invention, there is provided a laminated body obtained by laminating a plurality of sheets of an insulator having a conductor line formed on a surface thereof and integrally sintering the sheet, wherein the sheet having the conductor line is made of the insulator. A pair of coils electrically connected to each other through a through-hole provided in the multi-layered transformer, and a laminated transformer including a plurality of transformers formed by the pair of coils, wherein the transformers are stacked and arranged in the laminating direction. A multilayer electrode in which a shield electrode or a short ring electrode is arranged between each transformer, and external terminals connected to the pair of coils are provided on the outer surface of the multilayer body, and the external terminals are arranged next to each other. It is a continuous transformer.

According to a second aspect of the present invention, the conductor line is electrically connected to a laminated body having an insulating layer and a conductor line formed on an insulating substrate via a through hole provided in a sheet made of the insulator. A pair of coils, a laminated transformer having a plurality of transformers formed by the pair of coils,
The transformers are stacked and arranged in the stacking direction, and a shield electrode or a short ring electrode is arranged between the transformers, and the outer surface of the stacked body includes external terminals connected to the pair of coils, This is a stacked multiple transformer in which external terminals are arranged adjacent to each other.

In the present invention, it is preferable that an external lead electrode is formed on the shield electrode or the short ring electrode, pulled out to the side of the laminate, and connected to an external terminal for a ground line formed on the outer surface of the laminate. . It is also preferable that the conductor line formed on the sheet or the insulating layer is formed in a spiral shape of one or more turns. It is also preferable that the laminated multiple transformer of the present invention is a common mode choke coil array.

According to a third aspect of the present invention, there is provided a differential transmission cable using the laminated multiple transformer, wherein the differential transmission cable has two or more pairs of differential transmission lines, and each of the differential transmission lines Is a differential transmission cable connected to a pair of coils of the transformer. Preferably, the differential transmission cable has a ground line, and electrically connects the ground line with a shield electrode or a short ring electrode of the multilayer transformer. It is also preferable that a shield material for covering the differential transmission line of the differential transmission cable is electrically connected to a shield electrode or a short ring electrode of the laminated multiple transformer.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called multi-layer laminated transformer in which a short ring electrode or a shield electrode is provided between one set of transformers provided inside an insulator and another set of transformers. It is a thing. With this configuration, the magnetic flux generated when a signal is transferred to the transformer generates a counter electromotive force in the short ring electrode, and generates a magnetic flux in a direction opposite to the magnetic flux of the coil in the short ring. By canceling the magnetic flux leaking to the other transformer with the opposite magnetic flux generated in the short ring, magnetic coupling between the transformers is prevented as much as possible, or a shield electrode is provided to shield the magnetic flux from the shield electrode. In order to minimize the possibility of leakage of magnetic flux to other transformers, the harmful mutual interference between each transformer is suppressed, and the quality of signals that must be transmitted independently to individual circuits is reduced. I did not have it. In addition, by using a common mode choke array as the configuration of this transformer, it effectively functions as a countermeasure against skew noise of the differential transmission cable. The laminated multiple transformer of the present invention uses, for example, a Ni-Cu-Zn-based ferrite material, kneads this with a solvent or the like to form a paste, forms a sheet with a doctor blade, and forms Ag on the green sheet. A conductive paste as a main component may be formed by screen printing, appropriately laminated and integrally fired, or may be composed of Ni-Cu-Z.
An n-type ferrite material is powder-molded, and a conductor pattern to be an insulating layer and a transformer is formed on a magnetic substrate formed by sintering using a thin-film forming technique such as sputtering to form a laminated multiple transformer. Good. The insulator constituting the transformer is not limited to the Ni-Cu-Zn ferrite, but may be, for example, a Ni-Zn ferrite or a dielectric. Further, the coil, the short ring electrode and the shield electrode are not limited to those mainly composed of Ag, but may be anything having conductivity, but Ag or Cu having a small resistance value due to the configuration of the transformer.
It is desirable to use a conductor mainly composed of Further, in the multilayer multiple transformer of the present invention, an extraction electrode extending to the outside extending from the short ring electrode or the shield electrode is formed, pulled out to the side surface, and connected to an external terminal arranged on the outer surface. Configuration is preferred. When the shield electrode and the shield electrode are arranged on the differential transmission cable, they are electrically connected to the ground line and the shield material of this cable. The magnetic coupling can be further effectively reduced by flowing the leaked magnetic flux to the ground. It is preferable that the extraction electrode and the external terminal are as large as possible. Further, in the multilayered multiple transformer of the present invention, since the coil formed on one plane inside the insulator has one or more turns, a high-impedance coil can be produced without increasing the number of stacked layers, so that a low-profile coil is obtained. Is possible. In addition, since the number of laminations is small, man-hours can be reduced, and lamination displacement during lamination can be suppressed, so that an inexpensive transformer can be provided.

[0012]

(Embodiment 1) FIG. 1 shows an internal pattern configuration diagram of a laminated multiple transformer according to an embodiment of the present invention. Also,
FIG. 2 is a perspective view of the stacked multiple transformer. The laminated structure of this embodiment will be described in detail with reference to FIGS. The lower green sheet 1 has a conductor line pattern 1
1 is formed. One end of the conductor line pattern 11 faces the side surface and is connected to the external terminal 33c. The other end of the conductor line pattern 11 is a land. The green sheet 2 laminated thereon has a through hole 21 (hereinafter, a through hole is indicated by a black circle in the drawing) independent of the conductor line pattern 13. One end of the conductor line pattern 13 faces the side surface and is connected to the external terminal 34d. The other end of the conductor line pattern 13 is a land for a through hole. The independent through holes 21 are connected to the lands of the conductor line pattern 11. In the green sheet 3 laminated thereon, a through hole 22 independent of the conductor line pattern 12 is formed. One end of the conductor line pattern 12 becomes a through hole 25 and is connected to the through hole 21 of the lower layer 2, and the other end faces the side surface and is connected to the external terminal 37 c. Also,
The independent through holes 22 are connected to the lands of the conductor line pattern 13. On the green sheet 4 laminated thereon, a conductor line pattern 14 is formed. One end of the conductor line pattern 14 becomes a through hole 26 and is connected to the through hole 22 of the lower layer 3, and the other end faces a side surface and is connected to an external terminal 38 d. And these coils constitute one set to form one set of common mode choke coil. On the green sheet 5 laminated thereon, a short ring electrode pattern 19 is formed. Similarly, green sheets 6, 7, 8, and 9 are laminated, and a green sheet for protection is laminated on the green sheet 9 to form a laminate. The conductor paths 15 and 16 are connected by through holes 23 and 27 to form a coil between the external terminals 32b and 36b. Further, the conductor line patterns 17 and 18 are formed in the through holes 2.
4 and 28, and a coil is formed between the external terminals 31a and 35a. With these coils as one set, another set of common mode choke coils was formed. In the laminated multiple transformer of the present invention, two sets of common mode choke coils are arranged so as to be stacked in the lamination direction, and the common mode choke coil is divided into a magnetic circuit by the short ring electrode 19. Also, as shown in FIG. 3A, a lead line pattern 20 extending from the short ring electrode pattern to the outside is formed, pulled out to the side surface, and arranged on the outer surface of the multilayered multiple transformer shown in FIG. A sample connected to the external terminal 39e was also prepared. In the above two configurations, the pattern width of the short ring electrode (A in FIG. 1)
Ratio (A) to the width of the coil (B in FIG. 1).
/ B) was evaluated for the effect of suppressing mutual interference between the differential transmission transformers.

The effect of suppressing mutual interference was evaluated based on crosstalk between transformers. The evaluation method is based on the measurement method shown in FIG.
At D, the reference power is supplied to one of the coils, and 10 MH
The voltage V1 at z, 100 MHz was measured, the output side of the coil was terminated with a resistor, and the voltage V2 appearing at the output end of the other coil was measured and found by the following equation.

[0014]

(Equation 1)

FIGS. 6 and 7 show the evaluation results. FIG.
FIG. 7 is a diagram illustrating the relationship between the ratio of the short ring pattern width and the crosstalk at 10 MHz, and FIG. 7 is a diagram illustrating the relationship between the ratio of the short ring pattern width and the crosstalk at 100 MHz. The ratio of the width of the short ring electrode in the drawing is 0, which is a comparative example having no short ring electrode.

As a result, the width of the short ring electrode is preferably at least 1/5 of the width of the coil, more preferably 1/2.
That is all. Also, it has been found that the configuration in which the short ring electrode is connected to the ground is effective in suppressing harmful mutual interference at high frequencies. In the present embodiment, only one short ring electrode is used, but it goes without saying that the greater the number, the greater the effect of suppressing harmful mutual interference.

(Embodiment 2) A laminated type multiple transformer according to another embodiment of the present invention will be described. Since the structure of the stacked multiple transformer of this embodiment is almost the same as that of the first embodiment, only different portions will be described for simplification. In this embodiment, the shield pattern shown in FIGS. 3B and 3C is used. The characteristic point is that a shield pattern is used instead of the short ring pattern. In the present embodiment, the effect of suppressing mutual interference when the solid rate of the shield pattern was changed was evaluated by the same method as in the first embodiment. In addition, the solid ratio obtained by the following equation is used.

[0018]

(Equation 2)

FIGS. 8 and 9 show the evaluation results. FIG.
FIG. 9 is a diagram showing the relationship between the solid ratio of the shield pattern and the crosstalk at 10 MHz, and FIG. 9 is a diagram showing the relationship between the solid ratio and the crosstalk of the shield pattern at 100 MHz. The solid rate of 0 in the figure is a comparative example having no shield pattern.

As a result, the solid rate of the shield pattern is 3
It is preferably at least 0%, more preferably at least 50%. Further, it has been found that the configuration for connecting the shield pattern and the ground as in the second embodiment is effective for suppressing harmful mutual interference at high frequencies. When producing the shield pattern, it is better to produce the shield pattern area (the area (D1 × D2) in FIG. 3) larger than the coil pattern area (the area (C1 × C2) in FIG. 1). Needless to say.

Incidentally, the laminated transformer according to the present invention is not limited to the common mode choke coil array described in the above embodiment, and for example, the turns ratio is 1: 2 or 1: 3.
It is not necessary to form a plurality of sets of transformers having the same characteristics in one shape, and a plurality of sets of transformers having different characteristics may be formed. Also, the present invention
It is a method of inserting a shield pattern or a short ring pattern into a conventional laminated transformer, and a method of forming an external lead pattern on the shield pattern or the short ring pattern, pulling out to the side surface, and connecting to an external terminal for a ground line. The structure can be reduced in size and height without being restricted by the composition and manufacturing method of a certain material, and an inexpensive multilayer transformer can be provided.

(Embodiment 3) A differential transmission cable having two pairs of differential transmission lines was constructed using the laminated multiple transformer (common mode choke array) of Embodiments 1 and 2. FIG. 5 is a layout diagram showing a schematic configuration of a differential transmission cable for explaining an embodiment of the present invention. Although the differential transmission cable has a twisted differential transmission line 105 and a power supply line like a commercially available differential transmission cable such as IEEE1394. It is not shown in the figure to simplify the description. Also, the scale of each part is not accurate because it is schematically drawn to ensure visibility. FIG. 5 has the following configuration. The differential transmission cable 101 has connectors 102 arranged at both ends.
(Only one is shown in FIG. 5), at least two pairs of differential transmission lines 105, and a stacked multiple transformer (104A or 1A).
04B). Pin terminals 106 are fixed to each connector 102. At least two pin terminals 106 in the connector 102 are a pair of differential transmission lines 1
05, and at least two other pin terminals 106 in the other connector 102 are also connected to the other end of the pair of differential transmission lines 105. Then, the laminated multiple transformer (104A or 104B) was inserted at a predetermined position from at least one end of the differential transmission cable 101 to inside the differential transmission line 105 from inside the connector 102. The laminated multiple transformer 104B has a short ring pattern and a shield pattern, and a differential transmission cable in which these electrodes are electrically connected to a ground line and a shield material of the differential transmission cable was created. When these cables were evaluated, a differential transmission cable having reduced skew noise without deteriorating the signal quality could be obtained. In addition, the differential transmission cable in which the short ring pattern or the shield pattern is electrically connected to the ground line or the shield of the differential transmission cable has a superior effect of suppressing harmful mutual interference.

[0023]

As described above in detail, according to the present invention, harmful mutual interference between transformers is suppressed by minimizing magnetic coupling between transformers, and It is possible to provide an inexpensive stacked multiple transformer that can be reduced in size and height and that is inexpensive. Also,
By using a common mode choke coil array for the configuration of this multilayer transformer, differential transmission cables that handle multiple differential transmission signals can reduce skew noise without deteriorating signal quality. A differential transmission cable including a transmission line can be provided.

[Brief description of the drawings]

FIG. 1 is an internal pattern configuration diagram of a multilayered multiple transformer according to an embodiment of the present invention.

FIG. 2 is a perspective view of a multilayer transformer according to an embodiment of the present invention.

FIG. 3 is another internal pattern diagram of the multilayer multiple transformer according to the embodiment of the present invention;

FIG. 4 is a perspective view of another laminated multiple transformer according to an embodiment of the present invention.

FIG. 5 is a layout diagram showing a schematic configuration of a differential transmission cable according to an embodiment of the present invention.

FIG. 6 is a characteristic diagram of the multilayer transformer according to the embodiment of the present invention.

FIG. 7 is a characteristic diagram of the laminated multiple transformer according to one embodiment of the present invention.

FIG. 8 is a characteristic diagram of the laminated multiple transformer according to one embodiment of the present invention.

FIG. 9 is a characteristic diagram of the multilayer transformer according to the embodiment of the present invention;

FIG. 10 is a perspective view of a conventional laminated transformer.

FIG. 11 is a perspective view of a conventional multilayer transformer.

FIG. 12 is a perspective view of another conventional stacked multiple transformer.

FIG. 13 is a schematic diagram illustrating a method for evaluating crosstalk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Differential transmission cable 102 Connector 104 Stacked multiple transformer 105 Differential transmission line

Claims (8)

[Claims] 1. A laminated body obtained by laminating a plurality of sheets of an insulator having a conductor line on the surface and integrally sintering the sheet through a through hole provided in the sheet of the insulator. A pair of coils are connected to each other, and a stacked transformer including a plurality of transformers formed by the pair of coils, wherein the transformers are stacked and arranged in the stacking direction, and a shield electrode or A laminated multiple transformer in which a short ring electrode is disposed, and external terminals connected to the pair of coils are provided on an outer surface of the laminated body, and the external terminals are disposed adjacent to each other. 2. A pair of coils formed by electrically connecting a conductor line to a laminated body having an insulating layer and a conductor line formed on an insulating substrate through a through hole provided in a sheet made of the insulator. A stacked transformer including a plurality of transformers formed by the pair of coils, wherein the transformers are stacked and arranged in the stacking direction, and a shield electrode or a short ring electrode is arranged between each transformer, and An external terminal connected to the pair of coils is provided on an outer surface of the multilayer body, and the external terminals are arranged adjacent to each other. 3. An external lead-out electrode formed on the shield electrode or the short ring electrode, pulled out to a side surface of the laminate, and connected to an external terminal for a ground line formed on an outer surface of the laminate. The stacked multiple transformer according to claim 1. 4. The laminated multiple transformer according to claim 1, wherein the conductor line formed on the sheet or the insulating layer is formed in a spiral shape having one or more turns. . 5. The multi-layer transformer according to claim 1, wherein the multiple transformer is a common mode choke coil array.
5. The stacked multiple transformer according to any one of claims 4 to 4. 6. A differential transmission cable using the laminated multiple transformer according to claim 4 or 5, wherein the differential transmission cable has two or more pairs of differential transmission lines, and each of the differential transmission cables has a difference. A dynamic transmission line is connected to a pair of coils of the transformer. 7. The differential transmission cable according to claim 6, wherein the differential transmission cable has a ground line, and the ground line is electrically connected to a shield electrode or a short ring electrode of the stacked multiple transformer. The differential transmission cable described. 8. The differential transmission cable includes a shield material covering the differential transmission line, and electrically connects the shield material to a shield electrode or a short ring electrode of the multilayer transformer. The differential transmission cable according to claim 7, wherein